Hi guys!
Would love to hear your opinion on what to do

About 6 years ago I started to work as a contractor in ITS office at a University. After working there over a year I asked if I can be hired full time but they were only interested in keeping me as a contractor. I really wanted to have the security of a full time job and I applied and got hired in a smaller IT department at the same university. I worked there for over 4 years until the ITS manager invited me back for a full time position with a higher pay and I decided it would be a good decision to go back. I kept in contact with my former supervisors and co-workers and often come back just to talk and hang out. We're on very friendly terms.
I've been with ITS for almost a year but I missed my old job and honestly liked it better there, and the type of work I've been doing. Recently I found out that my old department has an open position for a Supervisor which will come with a significant pay increase, not to mention the title. I applied and got a call inviting me to an interview on Wednesday. I'm pretty confident that I can get the Supervisor position although it's not 100%.
Should I tell my current supervisor that I'm considering going back to my former department because they have a higher paying position I'm interested in? I almost feel like I will be abandoning him since he reached out to me directly when hiring me and offered me the job and I've spent less than a year working for him.
Thank you!!
Steve